Acrylonitrile is the basis for a family of important commercial polymers. For example, copolymers of butadiene with less than 50% acrylonitrile provide oil resistant polymers. Copolymers of alkyl acrylates with acrylonitrile provide a range of polymer products. For example when ethyl acrylate is the major component, oil resistant elastomers are obtained; and when acrylonitrile is the predominant comonomer, useful molded plastic materials are obtained. Copolymers of a major proportion of styrene and minor proportions of acrylonitrile are also useful in modifying vinyl chloride polymers, as moldable plastics and as components of ABS resin blends. Normally these acrylonitrile containing polymers are prepared by polymerization in water. Even when such polymerizations are substantially complete, there still remains undesirable amounts of unpolymerized acrylonitrile dissolved both in the polymer and the water. Normal procedures of stripping by vacuum or steam does not normally remove all of this undesirable acrylonitrile.